Diffusion

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Diffusion
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Diffusion

• The net movement of molecules from an area of
  high concentration to an area of low
  concentration.

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Concentration Gradient

• The measure of the difference in amount of
  molecules across a distance.

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Concentration Gradient

• Molecules naturally move down the concentration
  gradient.

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Concentration Gradient

• HIGH ? LOW

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Osmosis

• The diffusion of water across a membrane.

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Tonicity

• The relative solute concentrations of two fluids.

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Isotonic

• When the two solutions have equal amounts of
  solutes.

90 Water 10 Sucrose
90 Water 10 Sucrose
Solute Molecules
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Hypotonic Solution

• The solution with fewer solutes.

90 Water 10 Sucrose
Hypotonic Solution
80 Water 20 Sucrose
Solute Molecules
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Hypertonic Solution

• The solution with more solutes.

80 Water 20 Sucrose
Hypertonic Solution
90 Water 10 Sucrose
Solute Molecules
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How About Cells???

• What happens to cells in a
• Hypotonic solution?
• Hypertonic solution?
• Isotonic solution?

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What Should You NOT Do?
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Freshwater Aquarium
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Cytolysis

• Swelling
• In a Hypotonic Solution

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Problem!

• A paramecium lives in a hypotonic world.

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Hydrostatic Pressure

• The pressure of the cytoplasm against the cell
  membrane.

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Osmotic Pressure

• The pressure needed to counteract hydrostatic
  pressure.

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Turgor Pressure

• The pressure of a cell membrane against a cell
  wall.

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Plasmolysis

• Pulling away from cell wall.
• In a Hypertonic Solution

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Why do plants wilt?